Apparatus for processing a photosensitive medium

ABSTRACT

The improved apparatus for processing a photosensitive medium comprises a tank 1, having a substantially semi-cylindrical shape and provided with an input opening 1a and output opening 1b. 
     A transporting means 50 is provided above the tank 1, consisting of a pair of input rollers 51, a pair of output rollers 52 and a conveyor 53, fit to route a sheet 2 from the output opening 1b to the input opening 1a. 
     There are also provided an input guide 41 and an output guide 42, fit to guide the sheet 2 along a closed loop including the tank 1, or to the apparatus exit door.

TECHNICAL FIELD

The present invention relates to the technical field concerning theprinting of snapshots on a photosensitive medium.

Particularly, the present invention relates to an apparatus forprocessing a photosensitive medium, paper or film for instance, carryinga photographic image previously exposed therein.

BACKGROUND ART

It is known that reproducing images on a photosensitive medium, anegative photographic paper for instance, consists of placing said paperin a lightproof room, and then exposing it with light carryinginformation relative to the image to be reproduced.

Said light can be produced, for instance, by a lamp of a suitable powerand colour temperature; it is conveyed by an optical device, through afilm carrying a negative print of the image to be reproduced and then tothe photosensitive surface of the photographic paper.

According to further reproduction modes, equally known to a skilledtechnician, the photosensitive medium can consist of autopositivephotographic paper, either self-developing or not. It can be exposed bya light source that lights a film carrying the positive image, or by thelight directly coming from a subject to be photographed, by means of asuitable photographic camera.

At this point, the image is in a hidden state, and it is subsequentlydeveloped and made stable by submitting the photographic paper tosuitable chemical processes.

Said processes usually comprise the steps of immersing the photographicpaper into a first developing bath, for a first pre-defined period oftime, during which the image is developed; the paper sheet is thenimmersed into a second bath, containing a fixing or bleaching liquid,for a second pre-defined period of time. One or more immersions into awater bath follow, in order to remove the fixing traces. Thephotographic paper is then dried.

The above described developing process is carried out automatically byknown apparatuses, often with some variants and improvements.

Said apparatuses consist of a series of consecutively placed tanks, eachcontaining a suitable processing liquid, at a given temperature, and ofdragging members, fit to convey a photosensitive medium into said tanksaccording to a pre-defined timing. A continuous web made of the abovemedium, previously exposed with photographic images, is then insertedinto the developing tank first, then into the fixing or bleaching tank,and finally into the washing tank. The web is subsequently dried andcut, in order to separate each photogram.

Apparatuses like the one described above require, in order to operatecorrectly, that each tank is loaded with large quantities of therespective developing product. Said products must be replaced after agiven number of operating cycles, since their efficiency tends todecrease; otherwise, small quantities of new product have to beperiodically added to the exhausting product. Thus, it is very difficultto keep the physical parameters of the developing products constant,which is necessary to have a constant output quality. Moreover, it isdifficult to maintain a constant temperature inside the tanks, which isalso very important to achieve good quality printing results. Finally,power consumption is normally high, because big quantities of developingproducts must be thermoregulated.

A further apparatus for developing a single sheet of photosensitivemedium is also disclosed in the Italian patent Application N. B094A000481, in the name of the same Applicant. Said apparatus is of theso-called micro-tank or laminar tank type, and solves most of theaforesaid problems by using a developing tank having a very smallinternal volume, which is contained inside a thermoregulating device.

Said developing tank is fit to receive a sheet of photosensitive mediumto be processed inside a laminar hollow. It is fed in sequence withdeveloping products, fixing products and washing products, generally ina liquid state, by means of suitable, separate loading means. Eachproduct stays into the tank just for the time required to operateoptimally, after that it is flown out of the tank by means of drainingmeans. This latter is for instance made of a solenoid valve, connectedto a conduit, which conveys said products toward one or more draining orrecycling containers.

The photosensitive sheet is thus processed in a sequential way, by adeveloping cycle, eventually followed by one or more washing cycles, andthen by a fixing cycle, which is in turn followed by one or more tankwashing cycles.

The aforesaid device carries out the sheet processing operations in aneconomic, functional and completely automatic way but, since it workswith a single tank, it can suffer for some problems relating acontamination of the developing product by the fixing product. This canespecially happen because of undesired leakage of fixing productoccurring on the means for loading said product. Said leakage isgenerally due to some residual dripping from the output nozzle of saidloading means. Normally it is limited to one or two drips of fixingproduct but, if this happens during a developing cycle, the features ofthe developing product can be substantially modified.

Moreover the operation of said device is usually not very fast, since itcarries out the developing and fixing cycles in a sequential way,furthermore interposing one or more tank washing cycles in between.

A further micro-tank apparatus, disclosed in the Italian patentapplication N. B095A 000399, in the name of the same Applicant, isprovided with a pair of small-sized tanks, of the above described type,which are cascade-operating. One of those carries out the developingcycle, and the remaining one carries out the fixing and washing cyclesfor a sheet of photosensitive medium. This guarantees a better safetyagainst the developing product contamination, and speeds up theprocessing operations when several photosensitive sheets have to beprocessed. Indeed, with the above described apparatus, a subsequentphotosensitive sheet can be developed when a previous sheet is subjectto the fixing treatment.

The above described processing apparatuses don't attain completelysatisfactory operating results when the developing and fixing times arecomparable with the time required for inserting and taking out thephotosensitive sheet into and from the tank. In fact, because of thetime required for inserting or for taking out the sheet, the lowerportion of this latter stays into contact with the developing productsfor a longer time than its upper portion. Since the market now offersdeveloping products which allow a substantial reduction of thephotosensitive medium processing times, thus speeding up the wholeprocessing operations, said difference can lead to some visible effectson the processed photosensitive sheet.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to propose an improvedmicro-tank apparatus for processing a photosensitive medium whichguarantees a perfect processing homogeneity even when very fastprocessing products are used.

The aforesaid object is achieved by an improved apparatus for processinga photosensitive medium, comprising: at least a tank, featuring alaminar cavity fit to receive processing products for a sheet made ofphotosensitive medium, and to receive also said sheet, in order todevelop a latent image car ried by the same, said laminar cavity beingshaped like a rounded "U", having its concavity facing upwardly, theabove tank being also provided at its opposite ends with at least twoopenings, respectively an input opening, fit to receive said sheet, andan output opening, fit to allow said sheet to be transferred out of saidlaminar cavity; thermoregulating means, surrounding said tank and fit toregulate its temperature to a pre-defined value; loading means of saidproducts inside said tank; draining means of said products; guidingmeans of said sheet, fit to guide this latter into said tank and outtherefrom, the position of said guiding means being also adjustable toallow said sheet to be routed along a closed loop.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristic features of the invention are set out in thefollowing, with particular reference to the accompanying drawings, inwhich:

FIG. 1 shows a schematic sectional view of the apparatus of the presentinvention, during an input operating phase;

FIG. 2 shows a schematic view of the same apparatus, during a sheettransport operating phase;

FIG. 3 shows a schematic view of the apparatus, during an outputoperating phase.

MODE OF CARRYING OUT THE INVENTION

Referring now to said figures, numeral 1 indicates a tank suitably sizedfor arrange a sheet 2 made of photosensitive medium inside it, togetherwith a small quantity of processing products of known type.

Tank 1 is externally provided with known thermoregulating means 10,comprising a low thermal conductivity covering, combined with a laminarelectric resistor. This latter is fit to regulate the tank 1 temperatureto pre-defined values, which are optimised to allow a latent image,exposed with known techniques on a side of the sheet 2, to be developed.

Tank 1 is of substantially semi-cylindrical shape and it is provided, atits opposite ends, with an input opening 1a and with an output opening1b, both of those face upwardly. Said openings are wide enough to allowthe sheet 2 to enter the tank 1 from the input opening 1a and to exittherefrom from the output opening 1b.

The intermediate portion 3 of the tank 1, comprised between openings1a,1b is a laminar cavity which is shaped like a rounded "U", having itsconcavity facing upwardly (see, for instance, FIG. 1).

Near the input opening 1a and the output opening 1b, the tank 1 isfurthermore provided with loading means 20 of processing products. Saidmeans 20 consists of a nozzle for development liquid 21, which isconnected to a first measuring pump 21b, and then to a first container21c, by means of a first duct 21a; of a nozzle for fixing or bleachingliquid 22, which is connected to a second measuring pump 22b, and thento a second container 22c, by means of a second duct 22a; of a nozzlefor washing liquid 23, which is connected to a third measuring pump 23b,and then to a third container 23c, by means of a third duct 23a.

The tank 1 is also provided with draining means 30, fit to drain theprocessing products therefrom, placed at the lowest part of the laminarcavity 3 thereof. The draining means 30 consist of a draining valve 31,which is connected to a fourth container 31c by means of a fourth duct31a.

The aforesaid loading means 20 and draining means 30 are operated, in amutual phase relationship and according to known operating sequences, byan electronic control unit, not shown in the accompanying drawings, inorder to load and unload all the processing products.

Above the input opening 1a and the output opening 1b there is provided aguiding means 40 for the sheet 2, which comprises an input guide 41 andan output guide 42. The input guide 41 consists of a curved plate, thelower end thereof is placed immediately above the input opening 1a. Theinput guide 41 is pivotable about said lower end, and it is fit to bemoved between a sheet 2 input position A (see FIG. 1), wherein the upperend 41a of the input guide 41 is placed just above a cutter 8, thusallowing the sheet 2 to be guided toward the input opening 1a, and araised position B (see FIG. 2), wherein the upper end 41a is raised anddo not interferes with the sheet 2 path.

In a similar way the output guide 42 also consists of a curved plate,the lower end thereof is placed immediately above the output opening 1b,symmetrically with respect to the input guide 41. The output guide 42 ispivotable about its lower end, and it is fit to be moved between araised position C (see FIG. 1), wherein the upper end 42a is raised anddoes not interfere with the sheet 2 path, and an output position D (seeFIG. 3). When in this latter position, the upper end 42a of the outputguide 42 is placed near a pair of ejection rollers 9.

The operation of guides 41,42 is controlled by the aforementionedelectronic control unit, in a phase relationship with the operation ofthe loading means 20 and of the draining means 30.

Conveying means 50 is provided above the tank 1, fit to transfer thesheet 2, according to a pre-defined looping sequence, into the tank 1,then out of it, and then into the tank 1 again.

Said conveying means 50 comprises a pair of motor-driven,counter-rotating input rollers 51, a pair of motor-driven,counter-rotating output rollers 52, which are respectively placeimmediately above the input opening 1a and immediately above the outputopening 1b, and a conveyor 53, symmetrically arranged above the tank 1.

Said conveyor 53 substantially consists of a motor-driven roller 54,rotatably and symmetrically placed above the tank 1, and of a pluralityof freely rotatable small rollers 56, parallel with respect to theroller 54, whose external surface contacts the upper portion 54a of theexternal surface of this latter. The small rollers 56 are fit to guidethe sheet 2 along said upper portion 54a.

The operation of the conveying means 50 is also controlled by theaforesaid electronic control unit, in a phase relationship with theoperation of the loading means 20, draining means 30 and guiding means40.

The working of the present improved apparatus for printing of aphotosensitive medium is described in the following, from a startingcondition shown in FIG. 1, wherein a sheet 2, carrying a latent image tobe developed, is near the input opening 1a, after being cut by thecutter 8. Its front end is going to be engaged by the pair of inputrollers 51. The tank 1 has been previously filled with new developingproduct, by the first measuring pump 21b through its respective nozzle21. The input guide 41 is in its input position A, while the outputguide 42 is in its raised position C.

The pairs of counter-rotating rollers 51,52 are then activated, with apre-defined speed, according to a rotation direction which allows thepair of input rollers 51 to push the sheet 2 inside the tank 1, and thepair of output rollers 52 to rotate in the opposite direction. The sheet2 then contacts the aforesaid developing product, and goes out of thetank 1 from the output opening 1b, where it is engaged by the outputrollers 52.

In the meanwhile the draining valve 31 is activated, and the developingproduct is flown out of the tank 1. The second measuring pump 22b isthen activated, in order to fill the tank 1 with new fixing product.

At the same time, the input guide 41 is moved to its raised position B(FIG. 2), and the roller 54 is activated, according to a rotationdirection W. This allows the sheet 2 to be routed, with the co-operationof the small rollers 56, from the output rollers 52, along the upperportion 54a of the external surface of the roller 54, until it isengaged by the input rollers 51. The sheet 2 is then pushed again intothe tank 1 where, while passing thereinto, it is subjected to a fixingcycle, for a pre-defined period of time. It is then engaged again by theoutput rollers 52, and subsequently routed out of the tank 1.

At the same time the fixing product is drained from the tank 1, and thislatter is filled with a measured quantity of new washing product,usually clean water.

The sheet 2 is then engaged by the conveyor 53, and it is routed againinto the tank 1, where it is subjected to a washing cycle. The outputguide 42 is now moved to its output position D, and the sheet 2 isengaged by the output rollers 52 again and routed toward the pair ofejection rollers 9, and toward a drying device 7, of known type. Theinput guide 41 is then moved to its input position A, in order to allowa subsequent sheet 2 to be conveyed into the tank 1.

The washing product is finally drained from this latter, and it isfilled again with a new measured quantity of developing product.

Obviously, two or more sheet washing cycle and/or tank prewash cyclescan be performed if necessary, in order to completely eliminate thefixing product remains, which could contaminate the developing product.

The advantages arising from the present invention most of all consist inthat all the sheet 2 portions stay in contact with the developingproduct and with the fixing product for a perfectly equal period oftime. The duration of the developing and fixing cycles can be easilymodified by simply varying the rotation speed of the input and outputrollers.

What is claimed is:
 1. Improved apparatus for processing aphotosensitive medium, comprising: at least a tank (1), featuring alaminar cavity (3), fit to receive processing products for a sheet (2)made of photosensitive medium, and to receive also said sheet (2), inorder to develop a latent image carried by the same; thermoregulatingmeans (10), surrounding said tank (1) and fit to regulate itstemperature to a pre-defined value; loading means (20) of said productsinside said tank (1); draining means (30) of said products; guidingmeans (40) of said sheet (2), fit to guide this latter into said tank(1) and out therefrom; said apparatus being characterised in that saidtank (1) has said laminar cavity (3) shaped like a rounded "U", havingits concavity facing upwardly, and it is also provided at its oppositeends with at least two openings, respectively an input opening (1a), fitto receive said sheet (2), and an output opening (1b), fit to allow saidsheet (2) to be transferred out of said laminar cavity (3), the positionof said guiding means (40) being also adjustable to allow said sheet (2)to be routed along a closed loop.
 2. Apparatus according to claim 1,characterised in that said tank (1) is substantially shaped as asemi-cylinder.
 3. Apparatus according to claim 1, characterised in thatthere is also provided conveying means (50), fit to route said sheet(2), in a closed loop, inside the said tank (1), then out of said tank(1), and then inside the said tank (1) again, through said input opening(1a) and output opening (1b), for a pre-defined number of loops. 4.Apparatus according to claim 3, characterised in that said conveyingmeans (50) comprise at least a pair of counter-rotating input rollers(51), arranged immediately above said input opening (1a), at least apair of counter-rotating output rollers (52), arranged immediately abovesaid output opening (1b), and at least a conveyor (53), placed abovesaid tank (1) and fit to route said sheet (2) from said output opening(1b) to said input opening (1a), according to operating positions ofsaid guiding means (40).
 5. Apparatus according to claim 4,characterised in that said conveyor (53) comprises a roller (54),rotatably mounted above said tank (1), symmetrically with respect tothis latter, and a plurality of small rollers (56), free-rotatablymounted in contact with the upper portion (54a) of the external surfaceof said roller (54), being moreover mounted parallel andcounter-rotating with respect to the same roller (54) and being fit toroute said sheet (2) along said upper portion (54a).
 6. Apparatusaccording to claim 1, characterised in that said guiding means (40)comprises an input guide (41) and an output guide (42), consisting of apair of curved plates, symmetrically mounted above said openings (1a,1b)and pivotable about their lower ends.